(a) Field of the Invention
The present invention relates to a metallocene compound having a functional group that facilitates the preparation of a supported metallocene catalyst for olefin polymerization and the olefin polymerization using the same.
(b) Description of the Related Art
In 1976, Professor Kaminsky of Germany reported that olefin polymerization could be accomplished using zirconocene dichloride compound as a catalyst with a methylaluminoxane (MAO) as a co-catalyst which was obtained through partial hydrolysis of trimethylaluminum (A. Anderson, J. G. Corde. J. Herwing; W. Kaminsky, A. Merck, R. Mottweiler, J. Pein, H. Sinn, and H. J. Vollmer, Angew. Chem, Int. Ed. Engl. 15, 630 (1976)).
Thereafter, Exxon showed that the activity of a catalyst and the molecular weight of the produced polymer could be controlled by changing the substituents on the cyclopentadienyl ligand, and issued a patent (U.S. Pat. No. 5,324,800) on olefin polymerization utilizing the filed metallocene compounds with various substituent groups. A homogeneous metallocene catalyst shows unique polymerization characteristics which can not be obtained by conventional Ziegler-Natta catalysts. That is, molecular weight distribution of the produced polymer is narrow, co-polymerization is easy, and the co-monomer distribution is uniform. In the case of propylene polymerization, the tacticity of polymer can be controlled according to the molecular symmetry of catalyst. These unique characteristics not only opened up a way to produce new polymers which are not attainable by the conventional Ziegler-Natta catalyst, but also provided a way to make the tailor-made polymers. Accordingly, there has been continuous interest on this catalyst system.
In a gas phase or a slurry process, particle morphology and bulk density of produced polymer should be controlled to increase the mobility of polymer and the production rate per reactor unit volume. Also, the reactor fouling, a phenomenon that polymer sticks to reactor wall and agitator blades, should be avoided for a continuous operation. To solve these problems the catalyst should be anchored on a suitable support.
Described below are conventional preparation methods for supported metallocene catalysts.                (1) a metallocene compound is adsorbed on a support, and then activated by treatment with aluminoxane (W. Kaminsky, Makromol. Chem., Rapid Commun. 14, 239 (1993));        (2) aluminoxane is supported first, and then a metallocene compound is supported (K. Soga, Makromol. Chem. Rapid Commun. 13, 221 (1992); U.S. Pat. Nos. 5,006,500; 5,086,025);        (3) a metallocene compound is treated with aluminoxane, and then adsorbed on a support (U.S. Pat. No. 5,240,894); and        (4) the anchoring of catalyst is achieved by a chemical reaction between the ligand of a metallocene compound and a support.        
In one case, metal is ligated after ligand is supported. (K. Soga, H. J. Kim, T. Shiono, Makromol., Rapid Commun. 15, 139 (1994), Japanese Laid-open Patent No. Heisei 6-56928, U.S. Pat. No. 5,466,766). In the other case, a metallocene compound with suitable ligands is prepared and then it is supported onto a support by chemical reaction. The suitable ligands in this case usually contain silicon based functional groups such as alkoxysilane or halosilane (European Patent No. 293815, U.S. Pat. No. 5,767,300, European Laid-open Patent No. 839836, Korean Patent application No. 98-12660, and 99-06955). However, the metallocene compounds with silicon containing functional group are not easy to make and do not have good stabilities. For example, European Laid-open Patent No. 839836 discloses a metallocene compound having a functional group of —OSiMe3. The yield in the metallation step, which is the last step in synthesis, is only around 28˜51% which is a disadvantage in commercial application.
U.S. Pat. No. 5,814,574 discloses the supported polymerization catalyst which is prepared by the binding of inorganic support with metallocene compound containing a functional group selected from alkoxyalkyl, heterocycle oxygen radical, or alkyl heterocycle oxygen radical. U.S. Pat. No. 5,767,209 discloses a polymerization of olefins under a suitable temperature and pressure utilizing a supported catalyst. In this patent, the metallocene compound with Lewis base functionalities such as oxygen, silicon, phosphorus, nitrogen or sulfur atoms is bound to an inorganic support in the absence of aluminoxane to give a supported catalyst. However, the catalyst bound to and supported on an inorganic support surface by the Lewis acid-base reaction leaches out of the surface upon activation with Lewis acidic aluminoxane co-catalyst. The leaching of the catalyst will result in reactor fouling and irregular morphology which are detrimental in a slurry or a gas phase process.
Metallocene catalyst with a suitable functional group can be supported onto a silica surface by the reaction of alkoxysilane or halosilane functional group with surface hydroxyl group or highly reactive siloxane group, which is formed from the dehydroxylation of the silica above 600° C., as shown in Reaction Formula 1˜3.

EP 293815 A1 discloses a method in which a supported metallocene catalyst is prepared by the reaction of a metallocene compound containing —C—SiR2(OR′) functional group (wherein R is a C1-4 alkyl, C6-10 aryl, or C1-4 alkoxy, and OR′ is a C1-4 alkoxy) with a support hydroxyl group on its surface (See the Reaction Formula 4).
Herein, an Si—OR′ (silicon-based groups) bond of the metallocene compound is reacted with an Si—OH group of the support material to produce a strongly bound-supported metallocene catalyst via Si—O—Si bond formation. However, alkyl alcohol (R′OH) by-product is also formed during the reaction, which is possibly acted as a catalyst poison to lower activity of the final catalyst.
Especially, the Reaction Formula 3 is reported recently (J. Am. Chem. Soc. 117, 2112, (1995); J. Am. Chem. Soc. 115, 1190, (1993)) and is advantageous to the preparation of supported metallocene catalyst because side reactions are minimized (Korean Patent application No 98-12660). As mentioned above, however, the catalyst with siloxane functional group is not easy to make and has low stability. For example, the catalysts containing an alkoxysilane group, [HMe2Si—O—(CH2)6—C5H4]2ZrCl2 and [Me3Si—O—(CH2)6—C5H4]2ZrCl2], were disclosed in the examples and comparative examples of Korean Patent Application No 99-06955 which was applied by the present inventors. In the examples, the yield in the zirconation step which is the last step of the synthesis, was below 60% and the catalysts was observed to degrade slowly over an extended period under an inert gas atmosphere at room temperature.